3D printed guns are just one example of how we become more capable over time, not necessarily the only technology that people will use for violence. That sort of technology will continue to improve. Even if guns are banned, nothing stops a person from driving a truck through a crowd of people. The problem isn't the advanced technology; it's the people who use it maliciously.
US has a higher homicide rate than many other EU countries.
USA homicide rate is worse than many EU countries, but a bit lower than the world average. Who knows how much of it is cultural, and how much is biology?
